Index: firmware/App/Controllers/Heaters.c
===================================================================
diff -u -r9cc5da6947aa143a10f95519eb7f366c1b095d61 -rbaaf3dc55c2dee07d04efb97022fd2329a5bd73d
--- firmware/App/Controllers/Heaters.c	(.../Heaters.c)	(revision 9cc5da6947aa143a10f95519eb7f366c1b095d61)
+++ firmware/App/Controllers/Heaters.c	(.../Heaters.c)	(revision baaf3dc55c2dee07d04efb97022fd2329a5bd73d)
@@ -345,19 +345,19 @@
 
             if ( DG_PRIMARY_HEATER == heater )
             {
-                alarm    = ALARM_ID_RO_FLOW_TOO_LOW_WHILE_PRIMARY_HEATER_IS_ON;
-                measFlow = getMeasuredFlowRateLPM( RO_FLOW_SENSOR );
-                minFlow  = MIN_RO_HEATER_FLOWRATE_LPM;
+                alarm     = ALARM_ID_RO_FLOW_TOO_LOW_WHILE_PRIMARY_HEATER_IS_ON;
+                measFlow  = getMeasuredFlowRateLPM( RO_FLOW_SENSOR );
+                minFlow   = MIN_RO_HEATER_FLOWRATE_LPM;
+                isFlowLow = ( measFlow < minFlow ? TRUE : FALSE );
             }
             else
             {
-                alarm    = ALARM_ID_DIALYSATE_FLOW_TOO_LOW_WHILE_TRIMMER_HEATER_IS_ON;
-                measFlow = getMeasuredFlowRateLPM( DIALYSATE_FLOW_SENSOR );
-                minFlow  = MIN_DIALYSATE_FLOWRATE_LPM;
+                alarm     = ALARM_ID_DIALYSATE_FLOW_TOO_LOW_WHILE_TRIMMER_HEATER_IS_ON;
+                measFlow  = getMeasuredRawFlowRateLPM( DIALYSATE_FLOW_SENSOR );
+                minFlow   = MIN_DIALYSATE_FLOWRATE_LPM;
+                isFlowLow = ( measFlow - minFlow < NEARLY_ZERO ? TRUE : FALSE );
             }
 
-            isFlowLow = ( measFlow < minFlow ? TRUE : FALSE );
-
             checkPersistentAlarm( alarm, isFlowLow, measFlow, minFlow );
         }
         else